Thermal Expansion and Thermal Conductivity of Cesium Uranates.

Abstract

Two kinds of cesium uranates, which are often predicted by thermochemical calculations to be formed in irradiated oxide fuels with high oxygen potentials, were prepared from U3O8 and Cs2CO3 to determine the thermal expansions and the thermal conductivities. The lattice parameters of tetragonal Cs2UO4 and monoclinic Cs2U2O7 were measured by the high-temperature X-ray diffraction method as a function of temperature. The linear thermal expansions of Cs2UO4 and Cs2U2O7 obtained from the temperature dependencies of the lattice parameters were 1.2% and 1.1% from room temperature to 973 and 1,073K, respectively. The thermal diffusivities of Cs2UO4 and Cs2U2O7 were measured on the disk-shaped samples by the laser flash method as a function of temperature. The thermal conductivities were evaluated from the measured thermal diffusivities and the bulk densities, and the specific heat capacity available in literature. The thermal conductivity of Cs2UO4 corrected for 100%TD was 1.2W/m·K at 980K and that of Cs2U2O7 was...